[Essexeddie]

I have a problem with my starter motor on my 54 3100. Its slipping on certain sections of the ring gear. We have had the ring gear off and moved it round twice but still slips at TDC on certain cylinders (obviously the highest compression).
Should the starter motor be adjustable as mine isn't, it looks newish and 12v. Have I got the wrong starter motor which I believe is not running close enough to the ring gear causing it to slip?
It's bugging me. Any info would be great thanks.